The invention relates to an apparatus for treating body tissue, particularly soft surface tissue, with ultrasound. The apparatus comprises an ultrasound generation unit and an applicator with which ultrasound can be emitted from an applicator surface facing the body surface from the outside through the body surface into the body tissue.
The invention further relates to a method for treating body tissue, in particular soft surface tissue, with ultrasound. An apparatus as mentioned at the outset is known from the U.S. company brochure of Wells Johnson Company, Tucson, Ariz., U.S.A, entitled xe2x80x9cIntroducing SILBERG E.U.S.(trademark) External Ultrasonic Systemxe2x80x9d.
The use of ultrasound for healing purposes has increased in importance. Depending on the therapy, ultrasound is applied in the form of continuous or pulsed ultrasound wave fields.
Ultrasound has been successfully employed in so-called exterior shock wave therapy as well as ultrasound wave therapy for treating stones in the kidneys, urethra, gall and the like. An apparatus for treating body stones, a so-called lithotriptor, is known for example from the Swiss company brochure of Storz Medical AG, Kreuzlingen, Switzerland, entitled xe2x80x9cSTORZ MODULITH(copyright)-Systeme fxc3xcr die extrakorporale Lithotripsiexe2x80x9d. Short ultrasound pulses generated with this lithotriptor externally, i.e. outside of the body, are coupled into the body and focused on the stones in the body. The stones are localized beforehand by ultrasound imaging devices or X-ray systems.
Developments are being made in the external treatment of tumors in which special ultrasound applicators generate ultrasound waves which are transmitted to the tumor from the outside. By special control of the time the ultrasound acts on the tumor, an overheating of the tumorous tissue results and leads to its destruction.
It is not only the thermal effect of ultrasound which leads to dissolution of the cell structure, but also the pure mechanical effect in the form of cavitation. Sound waves propagate in a medium in the form of periodically varying density fluctuations of the medium. A volume element of the medium is alternately compressed (higher pressure) and expanded (lower pressure). The lower pressure can lead to vapor bubble formation in the fluid, for example in cell fluid, where in the end, the cell walls and/or the cell structure is destroyed.
It has been shown that this effect of ultrasound is suitable for disintegration or dissolution of soft tissue, for example fat tissue. The apparatus disclosed in the above-mentioned U.S. company brochure is employed for removing fat tissue close to the surface. The known apparatus comprises an applicator with which ultrasound is coupled from the outside through the body surface into the lower lying soft tissue.
A drawback of the known apparatus is the difficulty in achieving a uniform coupling of the applicator over its entire active surface to the tissue to be treated. When this is not the case, not only is the applied ultrasound energy not optimally utilized, an increased heat development also occurs.
A further drawback of the known apparatus is that it is not possible to control the depth effect of ultrasound, i.e. The penetration depth of the active ultrasound or its focus. When applying the applicator, a compression or a displacement of the underlying tissue can result, such that the individual tissue layers no longer have their original thickness or disposition. Without depth control, it is not possible to couple the ultrasound properly to the body tissue to be treated. There is also the danger that tissue which is not to be treated could be damaged.
Another apparatus of the present type for treating body tissue with ultrasound is disclosed in U.S. Pat. No. 5,618,275. The apparatus comprises an applicator having a housing in which an ultrasound transducer is embedded. A collar is provided on the housing on the side facing the body surface, which together with the housing forms a chamber of predetermined volume. A substance to be applied to the body surface is held in the chamber between the body surface and the applicator surface, such that the substance cannot be released from the chamber formed by the collar. The collar is formed of rubber or the like to be flexible. The therapeutic substance held by the collar between the applicator surface and the body surface more easily penetrates the tissue by means of the ultrasound treatment.
An object of the present invention is to provide an improved apparatus of the above-mentioned type, where ultrasound can be specifically coupled to the body tissue to be treated and where depth control of the ultrasound therapy can be achieved.
According to the present invention, an apparatus for treating body tissue, in particular superficial soft tissue, with ultrasound, is provided, comprising: an ultrasonic generation unit; an applicator having an applicator surface facing the body surface from which said ultrasound can be irradiated through said body surface into said body tissue, wherein a suction apparatus is provided for taking in said body surface against said applicator surface.
The present invention further provides a method for treating body tissue, in particular superficial soft tissue, with ultrasound, comprising the steps of: providing an ultrasonic generation unit and an applicator having an applicator surface; taking in said body surface against said applicator surface and irradiating said ultrasound from said applicator surface from outside through a body surface into said body tissue.
By taking in the body surface against the applicator surface, the underlying body tissue is drawn against the applicator, whereby a fixation of the tissue to the applicator is achieved. Through this fixation, the ultrasound can be optimally coupled into the tissue over its surface for the purposes of therapy. The treatment region in the body in terms of distance is fixed by sucking in the tissue. Thus ultrasound can be specifically applied to the body tissue in controlled manner because the distance between the emission point of ultrasound from the applicator and the body tissue is defined.
A sucking in of the body surface and thus the underlying tissue to be treated has the advantage over pressing the applicator onto the body surface in that the soft tissue underlying the surface is not displaced laterally or pushed outwardly. Thus the amount of soft tissue in the region of the applicator is not reduced, but on the contrary, it is drawn into the coupling region of the ultrasound.
In a preferred embodiment of the present invention, the suction apparatus is formed as a suction cup.
This can be realized by providing the applicator with at least one suction cup or forming the applicator itself as a suction cup in order to fix the tissue to the applicator. An embodiment of the applicator formed as a suction cup can be achieved by providing a lip structure at the edge of the applicator, which is flexible and elastic. When pressing the applicator onto the body surface, the lips produce a corresponding counter-force, whereby the body surface is drawn onto the applicator surface. Further, the lips must be configured such that they form a seal with the body surface either alone or together with a sealing substance, whereby the applicator itself should also be sealed.
In a further preferred embodiment, the applicator comprises at least one suction channel opening into the applicator surface, which is connected to an external suction device.
With this measure, a vacuum can be easily generated between the body surface and the applicator surface. A vacuum pressure is applied by the external suction apparatus to the suction channel joining into the applicator surface, whereby the body surface is sucked onto the applicator surface. The suction of the body surface can be further improved by providing a plurality of suction channels joining into the applicator surface. If only one suction channel is provided, it is advantageous to provide it approximately at the center of the applicator surface. The suction channel can also be connected to one or more open channels or grooves in the surface of the applicator.
In another preferred embodiment of the present invention, the ultrasound can be coupled into the body tissue by the applicator in a focused manner. By focused introduction of ultrasound into the body tissue, the ultrasound can be concentrated in a small volume element of only a few millimeters. The density of the focused ultrasound is increased by the concentration whereby the therapeutic effect is improved, namely the disintegration of the soft tissue. In addition, this allows one to work with a reduced energy density of the ultrasound, which leads to the further advantage that the energy density at the body surface is reduced and an extensive heating of the dermis is avoided. A focused introduction of ultrasound into body tissue is not possible in the apparatus mentioned above disclosed in the U.S. company brochure.
A focusing possibility exists, which is largely independent of the applicator surface, for example by the time dependence in driving the individual transducer elements of the applicator (phased array technique).
In a further preferred embodiment, the applicator surface is curved inwardly.
This has the advantage that the tissue is at least partially. sucked into the cavity thus formed. Depending on the suction effect, the tissue however can also be drawn into the cavity such that the body surface touches the applicator surface. A further advantage follows, particularly for use of the present apparatus for disintegration of soft surface tissue, that the soft tissue near the surface, i.e. especially the epidermis, dermis and fat tissue, can be sucked into the cavity, while the adjacent muscle tissue is less likely to follow due to its higher stability.
A further advantage of the inward curvature of the applicator surface is that the curved applicator surface can cause a focusing of the ultrasound based on its geometry. Another advantage is that the tissue surface, i.e. The surface skin and also the possible tissue transition surface, is normally larger in the sucked in condition than in the normal condition, so that the sound intensity and the undesired heating is reduced.
In a first preferred embodiment, the applicator surface has an approximately radial symmetric spherical cup shape.
A focusing or concentration of the ultrasound into a small volume of body tissue can be achieved with this configuration. By sucking the tissue into the applicator, the focus has a well defined position in the tissue at a well defined distance from body surface.
In a second preferred embodiment, the applicator surface has an approximately cylindric symmetric shape with an approximately U-shaped cross-section.
With this configuration, the ultrasound introduced into the tissue can be focused over the length of the applicator along a line. This has the advantage that a larger and longer surface of the tissue can be treated at the same time. Sucking in the tissue guarantees that the focus of the ultrasound is well defined along a line in the tissue over the length of the applicator.
In an alternative embodiment, the applicator surface is plane. Even with a flat surface, a depth control in the ultrasound therapy is guaranteed in conjunction with the suction apparatus. A focusing of the ultrasound using a planar or flat applicator surface can be achieved in that a phase controlled array of sound transmitters is employed.
In a further preferred embodiment of the present invention, the ultrasound generation unit comprises one or more electrically excitable transducer elements disposed in the applicator surface.
With this feature, the depth control in ultrasound therapy in conjunction with the body surface being drawn onto the applicator surface can be further improved, because the focus of the ultrasound in the body can be fixed with respect to distance by the sucking of the body tissue onto the transducer element. The coupling of the ultrasound into the body tissue is also improved. The transducer elements can be ultrasound transducers in the form of piezo-ceramic elements which generate ultrasound with the power density and frequency required for therapeutic purposes. When using several transducers, correspondingly distributed in the applicator surface, a geometric focusing of the ultrasound can be easily achieved when using a curved configuration of the applicator surface. A slight defocusing can also be achieved with a corresponding arrangement of the transducers or by a corresponding geometric shape of the applicator surface, which then enlarges the effective region of treatment and at the same time avoids overheating of the tissue.
Preferably, the transducer elements are excited with different frequencies and/or different phases.
This has the advantage that the position and extension of the focal region can be adjusted by driving the individual transducers with different frequencies and/or different phases instead of a geometric-electronic adjustment.
In a further embodiment of the present invention, the applicator is combined with a suction and irrigation apparatus for a fluid, which can be brought between the applicator surface and body surface and drawn off again.
Introducing a fluid between the applicator surface and the body surface during ultrasound therapy has the advantage that the body surface is cooled by the fluid. When focusing the ultrasound in the tissue to be treated, the ultrasound passing through the body surface causes a slight heating of the skin surface. This heating can be avoided by the fluid. Further, the introduced fluid has the advantage that it acts as a coupling medium between the applicator surface and the body surface and the ultrasound coupling into the body is improved.
Preferably, a suction channel for the fluid is provided which opens into the applicator surface in a center thereof.
The fluid can then be withdrawn centrally in the coupling region. On the other hand, this suction channel, when interrupting or throttling fluid flow into the region between the applicator surface and the body surface, can be used for sucking the body surface onto the applicator surface, whereby one channel can be saved.
It is also preferred that at least one inlet channel opens at the periphery of the applicator into a region between the applicator surface and the body surface.
This inlet channel can also have an annular configuration.
In conjunction with sucking off at a central region of the applicator surface, this feature has the advantage that fluid introduced from the side edges into the coupling region between the applicator surface and the body surface is well distributed in the coupling region.
In a further preferred embodiment of the present invention, the applicator comprises at its edge periphery a sealing, which forms a seal with the body surface.
On the one hand, this has the advantage that the suction effect when drawing in the body tissue is improved and on the other hand that fluid is securely held in the region between the applicator surface and the body surface. The sealing can comprise a seal strip provided along the circumference of the applicator surface.
In a further preferred embodiment, the depth of focus of the ultrasound in the body tissue is adjustable.
The depth control in a ultrasound therapy can be further improved and the thickness of the tissue layer to be treated can be accounted for. A focal depth corresponding to about half the thickness of the fat tissue layer appears to be favorable. A further advantage results from the adjustability in that one can avoid damage to the muscle tissue below the fat tissue if the penetration depth of ultrasound is too large.
In a further preferred embodiment, the distance between the one or more transducer elements and the body surface is adjustable.
Since the body""s surface substantially lies on the applicator surface due to the suction, or is in the direct vicinity, this feature provides the possibility of adjusting the depth of ultrasound focus in the body tissue.
Preferably, a spacer can be attached to the applicator. The spacer represents a simple possibility of altering the penetration depth of ultrasound into the body tissue. Furthermore, the curved chamber or cavity of the applicator can be effectively enlarged by the spacer, so that more tissue can be drawn into the cavity. With a planar applicator surface, a suction chamber can even be formed by using a spacer. As a further advantage, the spacer can simultaneously function as the mentioned sealing with respect to the body surface.
In a further preferred embodiment, the distance between the focus and the applicator surface is within a range of 5 and 40 mm.
With this focal distance from the applicator surface, the entire thickness of the soft tissue near the surface (epidermis, dermis, fat tissue) can be treated in advantageous manner.
In a further embodiment, the applicator comprises at least one ultrasound receiver element, which receives reflected ultrasound and converts same into an electrical signal, which is fed to an evaluation unit.
Due to the differing sound speed in fat tissue and muscle tissue, a partial reflection takes place at the transition layer between the soft tissue near the surface and the muscle tissue. This reflected sound can be received by the receiver element provided on the applicator. The distance between the fat/muscle transition layer and the body surface can then be determined from the reflected ultrasound and with this the thickness of the soft tissue layer close to the surface.
The determination of the position of this transition layer with respect to the body surface has the advantage that the depth control carried out in ultrasound therapy with the present apparatus can be further improved. By determining the depth of the transition between fat tissue and muscle tissue, the power or power density and also the focal depth of ultrasound in the tissue can be adjusted, namely such that no cell destruction occurs in the muscle tissue.
The ultrasound generation apparatus preferably includes at least one transducer element for generating ultrasound in the diagnostic power and frequency range in pulse-echo mode operation.
This can also be the mentioned ultrasound receiver element. While the reflected sound in therapeutic power and frequency range can be used to determine the depth of the soft tissue layer to be treated, the ultrasound in diagnostic power and frequency range, i.e. a relatively high frequency ( greater than 1 MHz) and lower power, is more strongly reflected at the tissue transi tion surface than sound in the therapeutic frequency range and therefore allows a higher resolution. With this, the opportunity is provided to control ultrasound therapy by monitoring the ultrasound, without the need for an additional ultrasound display device.
Pulse-echo operation means that the excitation of the transducer is pulsed such that sound pulses are emitted, where the transducer in the intermediate pauses acts as a receiver element for receiving reflected sound pulses. With this mode of operation, the advantage is achieved that only one transducer is sufficient for sending and receiving ultrasound to obtain a xe2x80x9cone dimensionalxe2x80x9d ultrasound image (A-image).
In a further preferred embodiment, the applicator surface has at least one temperature sensor element arranged thereon.
The temperature sensor, or a thermal-electric element, can measure the temperature on the body surface. The control of the ultrasound treatment is further improved in that the power of the ultrasound can be correspondingly adapted if a corresponding temperature increase is found at the body surface, i.e. The skin. In addition, if a temperature increase is determined as described above, a fluid can be introduced in the coupling region between the body surface and the applicator surface to cool the body surface.
In a further preferred embodiment, the applicator comprises at least one puncture channel.
This has the advantage that disintegrated soft tissue, optionally under ultrasound image control, can be removed or sucked out with a puncture needle introduced through the puncture channel.
It is also preferred that the applicator be provided with at least one electrode on its surface side for measuring the transition resistance between the applicator and the skin surface.
In conjunction with a suitable electric source, the transition resistance between the applicator and the skin surface can be measured locally with the electrode. If several electrodes are provided, the transition resistances between individual regions of the applicator and the corresponding regions of the skin surface can be locally measured, whereby regions of the skin can be found where the contact with the applicator is not optimal. In such a case, the suction action can be increased to achieve a uniform suction of the skin surface and the underlying soft tissue. The ultrasound power coupled into this region of the skin surface can also be reduced or for example a warning signal can also be initiated to recommend or to require a repositioning of the applicator. Thus local overheating of the skin can be avoided. The depth control of the present apparatus is also improved in this embodiment. It is advantageous to provide a plurality of electrodes between the transducer elements, so that local measurements of the transition resistance are possible over the entire therapeutic region of the applicator. The reference electrode necessary for the measurement is preferably provided at the edge of the applicator, for example at the circumferential edge of the applicator, however, it can be directly attached to the patient.
Naturally, the apparatus of the present invention can be employed in miniaturized form for therapy, in particular for endoscopic use.
Further advantages of the invention will become apparent from the following description in conjunction with the appended drawings.
It will be understood that the above-mentioned and following features to be discussed are not limited to the given combinations but apply to other combinations or taken alone without departing from the scope of the present invention.
Embodiments of the invention are illustrated in the drawings and will be discussed in more detail below.